Michigan police pulled over a car early Wednesday morning that was driving erratically and found a smoking methamphetamine lab in its trunk along with bomb-making materials, Reuters reported.

A police officer in DeWitt Township, near Lansing, reportedly approached the car and noticed one of the four passengers “holding a bag suspiciously,” a commander from Michigan Police told Reuters. Police eventually sent in a robot from the bomb squad, which found a box in the trunk that was smoking while it was being removed. A concealed weapon was also found in the passenger compartment.

Police said it appeared that the drug was cooking while the car drove up the road, reported Reuters. Three of the passengers were arrested.